"Regardless of body weight, (the findings) highlight the importance of counseling all women to participate in increasing amounts of regular physical activity and maintaining a healthy weight to reduce the risk of coronary heart disease," they concluded.

The study, appearing in the Archives of Internal Medicine, was based on information from a study of nearly 39,000 women that began in 1992 and traced a number of health issues.

The researchers said 34 percent of the women in the study were physically active based on government guidelines, 31 percent were overweight and 18 percent were obese.

In the end, 948 women were diagnosed with heart disease. Active women with normal weight had the lowest risk of developing heart problems while there was a slightly higher risk for those with normal weight who were not active.

The risk was next highest for active women who were either overweight or obese, and highest for similar women who were inactive.

Fat cells produce chemicals that can speed up hardening of the arteries and increase inflammation, the researchers said, harming blood vessels, while physical activity makes for healthier blood vessels and reduces the risk of blood clots.